Intersection: Not Closed
Proof:
Theorem: The family of CFLs is not closed under intersection.
• The intersection of some CFLs is not a CFL:
• L1 = {ambncn: m, n ³ 1} is a CFL
• L2 = {anbncm: m, n ³ 1} is a CFL
• L1 Ç L2 = {anbncn : n ³ 1} is not a CFL
  (proof based on the pumping lemma)
QED
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